The development of modern society promotes the rapid development of the mini-machines (1˜100 mm) and micro-machines (10 um˜1 mm), and micro-machines become one of mechanical frontiers. The core function of the micro-machines and micro-machines is to realize the transmission of low power and continuous motion in a tiny space.
The innovation research on working principle, performance characteristic and design and manufacture of the drive mechanism of micro-mechanism has been one of the important directions of the mechanical science frontier research field. In addition, the gear drive is a drive technology which is most widely used, and gears have formed an independent industry system, which is one of the important bases of the mechanical industry or even the modern industry and will accompany with the whole developing process of the industrial civilization. The design and manufacturing technology of new high-performance gear mechanisms is always one of the key research fields of the mechanical industry. As the most important characteristic of the tiny/micro mechanical and electronic products is small volume (which requires a small space of the drive mechanism and the drive system) and light weight, most of which primarily are based on the low power transmission or dividing movement rather than high power transmission, so that drive mechanisms (such as gear, chain, belt, connecting rod) widely applied in conventional industries usually are not suitable for this kind of products. Hence the key technology of the micro mechanical and electronic system field is to realize a drive method and mechanism for micro-machines.
All developed countries have vigorously carried out researches on the drive technology of micro-machines and made great achievements; in recent years, the drive technology of micro-machines has been widely applied. At present the drive technologies of micro-machines researched and developed by countries in the world mainly comprise:
(1). Mechanical drive technology by directly microminiaturizing drive mechanisms of the conventional mechanisms. For example, micro mechanical drive mechanisms such as micro-pump mechanism, micro-spring mechanism, micro-flow valve mechanism, micro-gear train mechanism, micro-parallel mechanism, micro-ratchet mechanism, micro-hydraulic drive mechanism. To directly microminiaturize drive mechanisms of the conventional mechanisms has some obvious disadvantages. For example, micro cylindrical gears have high requirements on manufacture and installation accuracy, have high costs and cannot realize the drive between the perpendicularly intersecting shafts; micro bevel gear drive cannot realize great transmission ratio, meanwhile the micro bevel gears are more difficult to be manufactured and installed; the micro-friction wheel drive needs an additional positive pressure applying device, has a complex structure, causes deformation of the shaft system and intensifies the friction and wear; the micro-worm drive takes an oversize space as the axes of the worm wheel and the worm are not in the same plane; the micro-screw drive has a low efficiency, causes wear easily and has crawling phenomenon at a low speed, etc.
(2) Micro-drive technology of non-conventional mechanisms. For example, electrothermal drive, giant magnetic and elastic drive, electroplating micro-drive, shape memory alloy (SMA) drive, heat mechanical drive, magnetic fluid drive, piezoelectric drive, artificial muscle drive based on non-pre-strain and non-conductive elastomer, micro-impact drive mechanism by exciting laser with lights etc. Among these non-mechanical micro-drive technologies, some have been applied in the industry, particularly the piezoelectric drive technology has been greatly applied in the industry. However, some have complex structures, are expensive and have unstable performances. The most important characteristic of the micro-drive technology of the non-conventional mechanisms is that it is only suitable for realizing small displacement or instantaneously triggering or intermittent drive of a micro power, and most of them are being studied.
(3) Combined or comprehensive micro-drive technology. For example, micro-macro or combining with connecting rod micro-drive; hybrid drive of gas drive and giant magnetostriction drive, etc.
(4) Drive mechanism of micro-machines by fundamental theory innovating based on drive mechanisms of the conventional mechanisms. In order to realize the micro power in a tiny space or continuous drive of the motion, as well as overcoming a series of problems caused by directly microminiatur zing the conventional drive mechanism, many scholars carried out fundamental theory innovation based on the drive mechanisms of the conventional mechanisms to research a new micro-drive mechanism. The research on the drive mechanisms of the micro-machines has originality features and belongs to one of the latest research fields at present.